National Radio Institute - 33 - Signal Analyzer
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Equipment:
33
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Information
For the convenience of those interested, o wiring diagram of
the Model 33 is shown in Fig. 1. To use your Signal Tracer
it is not necessary to refer to this schematic. However, as
you can see, this instrument is actually a special kind of
all«wave, tuned radio frequency (t.r.f.) receiver, complete
with audio amplifier end loudspeaker. Any on« of the
following four frequency
bands way be selected by the BAND SELECTOR switch.
Band A 170-490 kc.
Band B 490-1470 kc.
Band C 1470 kc.-3.9 me.
Band D 3.8-11.3 «c.
What is normally an antenna load is actual by the R.F.
probe, and any r.f. signals within the frequency range of
the instrument maybe fed into it through this probe. When
the R.F. probe is connected to a resonant circuit, very
little detuning will occur because of the 2 micro-microfarad
series condenser built into the probe handle. The COARSE
R.F. ATTENUATOR (SW-l) is a capacity type voltage divider
which controls the amount of signal fed to the first r.f.
amplifier tube. The FINE R.F. ATTENUATOR (Hj) controls the
bias, and hence the gain, of the first r.f. tube. The use of
these controls in making gain measurements will be described
later.
When the R.F. probe is used, the tuning eye indicates the
relative strength of the signal reaching the 6SQ7 diode
detector plate (pin No. 4). After demodulation, the audio
signal passes on through the a.f. amplifier section to the
loudspeaker. when the HF-AF switch is in the A.F. position,
it disconnects the r.f. amplifier and makes it possible to
use the audio section of the Signal Tracer independently. In
this case a.f. signals are fed through the A. F. probe and
blocking condenser C29 *.© the calibrated volume control
(A.F. ATTENUATOR), and are amplified and reproduced by the
loudspeaker. The method of using the calibrated markings on
the A. F. ATTENUATOR to measure a.f. gain is discussed
later. Part of the amplified signal is fed back from output
transformer Tj and rectified by the other diode plate of the
6SQ7 (pin No. 5). This rectified voltage is used to close
the tuning eye to indicate the relative strength of the a.f.
signal being examined.
While the over-all sensitivity of the Model 33 is
exceptionally high for on instrument of this type, there is
no attempt made to keep the sensitivity constant with
variations in frequency. To do so would add considerable
coat to the instrument. However, as gain measurements are
generally made at a single frequency, this proves to be no
drawback.
Service and user manual
Manual type:
Service and user manual
Pages:
18
Size:
2.9 MB
Language:
english
Revision:
Manual-ID:
Date:
Quality:
Scanned document, reading partly badly, partly not readable.
Upload date:
Oct. 3, 2016
MD5:
d04ff17e-eec8-e51f-c8dd-ba7422d0af8f
Downloads:
603